sql中or语法介绍

1.mysql中or语法的使用,在mysql语法中or使用注意点。 

  $sql = 'SELECT                   *               FROM                   `vvt_spread_doubleegg_exchange_award` AS p              WHERE                  p.`act_type` = 4 or p.`act_type` = 5              AND                  p.`user_id` = ' .$user_id              ;

sql中的or语法一般用于多个条件的查询,上面的语法查询的相当于:两个sql查询出来的数据集合。

<span style="color: #000000">  $sql = 'SELECT *  FROM  `vvt_spread_doubleegg_exchange_award` AS p WHERE  p.`act_type` = 4;<br><span style="color: #000000">$sql = 'SELECT * FROM `vvt_spread_doubleegg_exchange_award` AS p WHERE  <span style="color: #000000">p.`act_type` = 5 AND p.`user_id` = ' .$user_id</span>;</span></span>

2.  要想查询act_type = 4  and user_id = 11123 或者等于 p.`act_type` = 5 and user_id = 11123的数据集合 or两边的条件一定要加()。

  $sql = 'SELECT                   *               FROM                   `vvt_spread_doubleegg_exchange_award` AS p              WHERE                  (p.`act_type` = 4 or p.`act_type` = 5)              AND                  p.`user_id` = ' .$user_id              ;

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